Positive results in psychology can behave like rumours: easy to release but hard to dispel. They dominate most journals, which strive to present new, exciting research. Meanwhile, attempts to replicate those studies, especially when the findings are negative, go unpublished, languishing in personal file drawers or circulating in conversations around the water cooler.

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Psychology is not alone in facing these problems. In a now-famous paper, John Ioannidis, an epidemiologist currently at Stanford School of Medicine in California argued that “most published research findings are false”, according to statistical logic. In a survey of 4,600 studies from across the sciences, Daniele Fanelli, a social scientist at the University of Edinburgh, UK, found that the proportion of positive results rose by more than 22% between 1990 and 2007. Psychology and psychiatry, according to other work by Fanelli, are the worst offenders: they are five times more likely to report a positive result than are the space sciences, which are at the other end of the spectrum.